The proposed work is designed to study the metabolic effects of Chloromycetin on human bone marrow cells in an attempt to provide an explanation for bone marrow depression from this drug. The hypothesis is being tested that Chloromycetin-induced bone marrow aplasia results from a biochemical predisposition perhaps genetically determined. Evidence has been provided in the past year from this laboratory that reversible bone marrow suppression from Chloromycetin is the consequence of the mitochondrial injury. Further investigation along these lines is in progress.